WASHINGTON — The Trump administration is preparing to dismantle key Obama-era limits on drone strikes and commando raids outside conventional battlefields, according to officials familiar with internal deliberations. The changes would lay the groundwork for possible counterterrorism missions in countries where Islamic militants are active but the United States has not previously tried to kill or capture them.

President Trump’s top national security advisers have proposed relaxing two rules, the officials said. First, the targets of kill missions by the military and the C.I.A., now generally limited to high-level militants deemed to pose a “continuing and imminent threat” to Americans, would be expanded to include foot-soldier jihadists with no special skills or leadership roles. And second, proposed drone attacks and raids would no longer undergo high-level vetting.

But administration officials have also agreed that they should keep in place one important constraint for such attacks: a requirement of “near certainty” that no civilian bystanders will be killed.

The proposal to overhaul the rules has quietly taken shape over months of debate among administration officials and awaits Mr. Trump’s expected signature. Despite the preservation of the protections for civilians, the other changes seemed likely to draw criticism from human rights groups.

The policy paves the way for broader and more frequent operations against Al Qaeda, the Islamic State and other jihadists. It would also apply in countries where the United States has targeted Islamist militants outside of regular combat for years, including Yemen, Somalia and Libya, and would ease the way to expanding such gray-zone acts of sporadic warfare to elsewhere in Africa, Asia and the Middle East where terrorists operate.

The policy, while containing significant changes, also preserves a key structure of President Barack Obama’s approach to counterterrorism: dividing the world into war zones and places where higher protections for civilians apply. The elements of continuity suggest that as the war on terrorism drifts toward its 17th year, political, legal, diplomatic and practical hurdles constrain the Trump administration from making more radical policy shifts.

“The killers need to know they have nowhere to hide, that no place is beyond the reach of American might and American arms,” he said. “Retribution will be fast and powerful.”

In May 2013, Mr. Obama imposed the rules on kill-or-capture operations by the military or the C.I.A. outside war theaters like Afghanistan, Iraq and Syria. The plan would extend Mr. Trump’s pattern of giving broader day-to-day authority to the Pentagon and the C.I.A. — authorizing the agencies to decide when and how to conduct high-risk counterterrorism operations that Mr. Obama had insisted be used sparingly and only after top officials across the government reviewed them.

The move would also grant a C.I.A. push for permission to expand its program of covert drone strikes, which has included occasional attacks in Yemen and Syria but has largely centered on the tribal region of Pakistan, to Afghanistan — until now the exclusive purview of the military.

A cabinet-level committee of the top leaders of national-security agencies and departments approved the proposed new rules — called the P.S.P., for “Principles, Standards and Procedures” — at a meeting on Sept. 14 and sent the document to Mr. Trump, the officials said. They spoke on the condition of anonymity to describe sensitive discussions about a policy that is not yet final or public. A spokesman for the National Security Council did not contest their account but declined to comment.

One senior administration official described the proposed changes as primarily aimed at making much of the “bureaucracy” created by Mr. Obama’s 2013 rules, the Presidential Policy Guidance, or P.P.G., “disappear.”

The official argued that the replacement rules should be seen as similar to Mr. Obama’s but clearer and less bureaucratic — meaning drone operators and commanders would face fewer internal hurdles to launching specific strikes or raids.

By clearing the way to target rank-and-file Islamist insurgents even without the presence of a high-level leader focused on attacking Americans, the new approach would appear to remove some obstacles for possible strikes in countries where Qaeda- or Islamic State-linked militants are operating, from Nigeria to the Philippines.

However, the new plan would still require higher-level approval to start conducting strikes or raids in new countries under “country plans” that would be reviewed every 12 months. And under international law, the United States would probably also still need to obtain consent from a country’s leaders to use force on their soil to strike at lower-level militants who pose no direct threat to the United States, weakening any self-defense argument.

Even before Mr. Obama left office, the evolving terrorism threat put pressure on the limits that were imposed in 2013. At the time, Al Qaeda was still reeling from the killing of Osama bin Laden, combat troops had left Iraq and were being reduced in Afghanistan, and operations outside war theaters seemed destined to be limited to occasional airstrikes aimed at individual “high-value targets” in Pakistan and Yemen, such as Qaeda leaders.

But the Islamic State has arisen and spread in the years since, and the military, especially while partnering with local governments, has found ways to get exceptions to Mr. Obama’s rules — winning temporary exemptions to strike in various regions or justifying airstrikes on groups of lower-level militants as a matter of self-defense.

Several Obama administration counterterrorism officials had been bracing for a more complete dismantling of their handiwork, and they offered tentative praise for the prospect that their successors will keep in place heightened standards to protect civilians outside war zones. They had argued that avoiding bystander deaths was crucial not just for humanitarian reasons, but also to maintain support among allied governments and local populations and to keep from fueling terrorist propaganda and recruiting.

If the requirement of near certainty that no civilians be killed remains in place, “that’s a real testament to the fact that it was not political or Obama being overly concerned about human rights; preventing civilian casualties is something our operators have seen as really important,” said Luke Hartig, a senior director for counterterrorism at the National Security Council during the Obama administration.

It remains to be seen whether Mr. Trump will sign off on keeping the protections for civilians. During deliberations, some officials had argued for more leniency, but administration officials decided the risks outweighed the benefits.

International law governing war or self-defense allows countries to knowingly kill some civilians as an incidental consequence of attacking a legitimate military target, so long as the bystander deaths are deemed necessary and proportionate.

But some international law scholars, European allies and human rights groups disagree with the United States’ position that war zone rules — like a right to attack militants based only on their status as enemy fighters, even if they do not pose a literally imminent threat at that moment — apply to counterterrorism strikes outside conventional battlefields.

Zeke Johnson, senior director of programs for Amnesty International USA, objected to the prospect of Mr. Trump eliminating the requirement that individual targets each pose a threat to Americans.

“The Obama administration’s policy guidance on the use of lethal force was a positive step but fell far short on human rights protections,” he said. “Any decision to weaken those standards would be a grave mistake.”

The updated rules would continue to limit such strikes to members of groups that the executive branch has deemed to be covered by the aging congressional Authorization for Use of Military Force against the perpetrators of the Sept. 11 attacks, including Al Qaeda, the Islamic State and their associated forces.

Earlier this year, Mr. Trump agreed to a Pentagon request to exempt large swaths of Yemen and Somalia from the 2013 rules by declaring them to be “areas of active hostilities,” temporarily bringing them under less restrictive war-zone rules. However, the head of the military’s Africa Command, Gen. Thomas D. Waldhauser, decided on his own to keep the targeting limit of near-certainty that no civilians would die for strikes in Somalia.